Elapsed time metering system



Jan. 26, 1932. N. H. SAUNDERS 1,842,805

ELAPSED TIME METERING SYSTEM Filed April 9, 1930 5 Sheets-Sheet l NurmanEBLITZCZEFS 5 0 Jan. 26, 1932. N. H. SAUNDERS 1,842,805

ELAPSED TIME METERING SYSTEM Filed April 9, 1930 5 Sheets-Sheet 2 s4lWA/G BA CK TONE ]nuaninr NDFTUEH SEUFZHEPE' Jan. 26, 1932. N, SAUNDERS1,842,805

ELAPSED TIME METERING SYSTEM Filed April 9, 1930 5 sheets-Sheet 3o/Ffimlm;

T0 OPEPS TELEPHONE 4 win N urman HSaundsrs Jan. 26, 1932. N. H. SAUNDERS1,842,805

ELAPSED TIME METERING SYSTEM Filed April 9, 1930 5 Sheets-Sheet 4 7%%Hit Jan. 26, 1932. I SAUNDERS 1,842,805

ELAPSED TIME METERING SYSTEM Filed. April 9, 1950 5 Sheets-Sheet 5 Ln ia MAEG/A/AL k I H I /42 H -Inuaniur' NarmanHSaunders Patented Jan. 26,1932 UNITED s'rrss PATENT QFFEE NORMAN SAUNDERS, OF I-IOIVIEWQOD,ILLINOIS, ASSIGIQ'OR, BY MESNE ASSIGNMENTS, TO ASSOCIATED ELECTRICLABORATORIES, TING, OF OHICAGG, ELLINOIS, A CORPORA TION OF DELAWAREELAPSED TIME METERING SYSTEM Application filed April 9,

The present invention relates to elapsed time metering in general, butis concerned more particularly with elapsed time metering semi-automatictelephone systems, in which calls are extended through the medium ofautomatic switches controlled from an operators position.

The principal object of this invention, briefly stated, is the provisionof new and improved circuit arrangements whereby a calling subscribermay be charged for all calls, regardless of whether or not those callsare completed, according to the time the call-- ing subscribers receiveris off of the receiver hook, the charge being assessed at intervalsdurin that time.

A Ieature of the system, provided in accordance with saidprincipal'object, is an arrangement whereby, when a busy condition isencountered at any time during the establishment of the connection, abusy signal is transmitted from the trunk equipment associated with thefirst switch of the switch train, and whereby all of the switchessucceeding the trunk equipment are released for use of other callingsubscribers.

Another feature is the arrangement whereby the operators impulse senderis released, when a busy condition is encountered, without it beingnecessary for that sender to complete the sending of the remainingdigits.

Other objects and features having to do with the refinement of thevarious circuits peculiar to a system of this character but not beingspecifically pointed out now, will be readily apparent from a perusal ofthe description to follow, reference being had to the accompanyingdrawings comprising Figs. 1 to 5, inclusive, which, when arranged withFig. 2 to the right of Fig. 1, Fig. 3 directly below Fig. 1, and Figs. 4and 5 to the right of Fig. 8, show by means of the usual circuitdiagrams suflicient of the apparatus employed in a system embodying theprinciples of the invention to enable a complete understanding thereofto be had.

General description The equipment shown in Fig. 1 includes thesubscribers station A, the line of Wl11Cl1 1930. Serial No. 442,829.

terminates at the exchange in the automatic lineswitch G which hasaccess to trunks among which is the trunk comprising conductors 1 to 3,inclusive. Individual to this trunk is a trunk relay group RG and aselector switch D, and it is through this trunk relay group thatconnection is established between the calling subscriberand theoperator, and through which the operators sending equipment operates theselector D to ext id the connection. It is through the relay group HGthat the calling subscribers elapsed time meter M is operated whenconnection is made with the trunk 13 by the subscribers lineswitch C.

Thelineswitch C is mechanically of the well known rotary type in whichthe wipers have no normal position, remain in thelast position in whichthey were last used, and move in a forward direction only.

The meter M may be considered as representing any of the well knowndevices whereby the reversal of current through a magnet results in theoperation of a registering means. A meter of this type is shown inUnited States Letters Patent, No. 912,268, issued to Charles M. Beattie,under date of February 9th, 1909.

The selector D is mechanically of the well known vertical and rotarytype in which the bank contacts are arranged in horizontal rows orlevels accessible to the switch wipers which are carried by the switchshaft, which shaft is elevated in a step-by-step motion in accordancewith the impulses received by the selector to position the wipersopposite the corresponding level, and which is then automaticallyrotated to position the wipers in engagement with a set of contacts inthat level associated with an idle trunk leading to the next switch inthe train.

Associated with the trunk relay group HG is a sender-selector switch SS,the function of which is to select an idle operators impulse sender andassociate .that sender and the operators .telephone equipment with thetrunk 13.

The apparatus shown in :Fig. 2 of the drawings is the connector E andthe ringing frequency selector RFS. This connector E is mechanically thesame as the selector D, Fig. 1, except that the switch shaft isdirectively controlled in its rotary motion, that is, is rotated anumber of steps in accordance with the second series of impulsesreceived by the connector. The connector E by being provided with theringing frequency selector RFS is adapted for use in telephone systemshaving ten-party lines.

The ringing frequency selector RFS is mechanically of the well knownrotary type of switch whose wipers have a normal position and areadvanced therefrom in a stepby-step motion by the operating magnet 79.The operation of the release magnet 80 causes the wipers to return totheir normal positions.

The apparatus represented by the rectangle P, Fig. 1, and the rectangleP1, Fig. 2, may each be considered as a continuously operating device bymeans of which the polarity of the two associated conductors is reversedat predetermined intervals. As will be more clearly explainedhereinafter, the said conductors serve as a source of battery feed forthe calling line and in order that there need be no interruptions of theundulatory voice currents which may be traversing the line, theapparatus is arranged to gradually decrease the potential andsubsequently increase it gradually to the maximum voltage. A device ofthis kind is shown in the aforementioned Beattie patent.

The apparatus shown in Figs. 3, 4 and 5 includes the operatorssender-control key set and associated relays, and one of four senders.The portion of the sender shown in Fig. 3 includes the relays 111 to114, in elusive. The registering portion of the sender is shown in Fig.4, while the sending portion is shown in Fig. 5.

The layout of the apparatus is such that each semi-automatic operatorsposition is provided with four senders similar to that shown in thedrawings. The sender-selector SS, Fig. 2, which is usually a 25 positionmechanism, has access to senders of several operators positions.

- Although the system as shown in the drawings involves the use of onlya first selector and a connector, second and even third selectors may beplaced between the selector D and the connector E. In that case,selectors like selector D will be employed.

Detailed description The apparatus having been described generally inthis manner, it will now be described in detail as to its operation. Forthis purpose, it will be assumed that the subscriber at substation A,Fig. 1, desires a connection to be set up from his line to the line ofanother subscriber, whose number is, for example, 7945, it beingremembered that this subscriber is one of ten subscribers who are on thedesired line and whose telephone numbers differ only in the last digitwhich is the ringing-code selecting digit.

When the receiver is removed from the receiver hook at station A, thelineswitch C, the circuits of which are not shown, operates in the usualmanner to select an idle trunk,

which trunk, it will be assumed, is the one comprising conductors 13.WVhen this trunk is seized, battery feed relay 8 of the trunk relaygroup RG operates over the calling line and at its armature 9 completesthe obvious circuit for slow-to-release relay 10. Relay 10 operates whenits circuit is closed and at its armature 11 connects ground to therelease trunk conductor 3, so as to guard the trunk line from intrusionand to main tain the lineswitch C operated, and at its armatures 12 and13 connects the test wiper of the sender selector SS to the motor magnetMM thereof.

The connection of ground to the releasetrunk conductor 3 completes thecircuit of relay 17 by way of armature 15 and resting contact of relay14, lower winding of relay 17, armature 13 and make contact of relay 10,interrupter springs of motor magnet MM, and winding thereof to battery.However, if the wipers of the sender selector SS are in engagement withcontacts associated with a busy sender, ground will be present on thecontacts with which the test wiper is in engagement. This ground willshort circuit relay 17 before it has had a chance to operate, and willsupply direct ground to the motor magnet MM through the interruptersprings thereof.

Sender selection When direct ground is so fed to the motor magnet MM ofthe sender selector SS, the motor magnet will operate and advance itswipers into engagement with the next set of contacts of its bank. If thesender associated with this set of contacts is also busy, the test wiperwill again encounter ground and the motor magnet will again operate toadvance the sender selector wipers into engagement with the next set ofbank contacts. This action will continue until the test wiper engages acontact to which no ground is connected.

Assuming that the trunk line comprising conductors 24 to 28, inclusive,and extending to the sender shown in Figs. 3, 4 and 5, is the one foundto be idle, switching relay 17, which is short-circuited as long asground potential is encountered by the test wiper of the sender selectorSS, energizes in series with the motor magnet MM. The motor magnet,because of the relatively high resistance of relay 17, does notoperatively energize in series therewith.

At armatures 18 and 22, relay 17 when so energized connects the talk and-l-talk wipers, respectively, of the sender selector SS to the negativeand positive conductors 1 and 2 of the trunk line, thereby extendingthose conductors into connection with the negative conductor 24 and thepositive conductor 25 extending to the selected sender. At armature 19,relay 1.7 connects the switch ing conductor and the switch wiper to thewinding of relay 4. At armature 20, relay 17 disconnects the test wiperfrom the junction of the winding of relay 1'? and the motor magnet MM,and connects the wiper to ground, therebv placing a guarding and holdingpotential upon conductor 26. At armature 21, relay 1'? connects itsupper lowresistance winding in series with its lower high-resistancewinding to insure its being held perated. At its armature 23 relay 1'?connects the impulse conductor 28 through the impulse wiper of thesender selector SS, t0 the positive line conductor of the selector D.

In the selected sender, relay 111 operates over the grounded releasetrunk conductor 26, and through contacts of relay 112, and at its lowerarmature disconnects the corresponding test conductor from ground and extends it to the #1 sender connecting relay 108. This is preparatory toenabling the dis tributo-r switch DS to stop on a contact associatedwith the #1 sender and operate the #1 connecting relay 108, so as toconnect the #1 sender with the operators equipment. At its upperarmature, relay 111 places ground upon the associated start-operatingslow-acting relay 116 through contacts of relays 105-108. Relay 116closes a circuit for the associated relay 115, which relay operates andstarts the hunting action of the distributor switch DS by connecting thetest wiper 125 to stepping magnet 12 1 through the self-interruptingcontacts of the stepping magnet. At its two upper armatures, relay 115disconnects common conductors 118 and 119 from the operators telephoneset and connects the conductor 119 through the associated condenser tothe differential tonegenerating relay 110.

Each time relay 110 pulls up and closes the circuit for its upperwinding in parallel with its lower winding, it falls back due to thedifferential relation between its two windings, thereby generating atone current which is impressed upon conductor 119 through theassociated condenser. This tone current is not sent back to the callingline for the time being.

The test wiper 125 of the distributor switch DS encounters groundpotential on the test contacts of each sender not in calling conditionowing to the fact that the relay corresponding to relay 111 in eachsender not in a calling condition is deenergized and has a groundpotential placed upon the corresponding test conductor at its lowerarmature.

When the wiper 125 of the distributor switch DS arrives on a contactassociated with the calling sender, the first contact or the fifthcontact, the stepping operation ceases due to the absence of a directground potential on the test conductor. A circuit is then closed forrelay 108 through the test wiper 125 and the lower armature of relay 111from battery through stepping magnet 12 1v and the lower contacts ofrelay 115. Magnet 121 does not operatively energize in series with relay108 owing to the relatively high resistance of the latter. When relay108 operates, it connects, at certain of its lower armatures, the sixconductors associated with the operators key-set, to the correspondingconductors of the sender; it closes a locking circuit for itself at itsinner lower armature in multiple with the lower contacts of relay 115;it lights the call lamp associated with the operators key-set at itsupper armature; it connects up the conductors 2 1 and at itsintermediate upper armatures to the common conductors 118 and 119; andat its innermost upper armature it opens the circuit of slow-actingrelay 116.

During the time required for relay 116 to fall back after its circuit isopened, the tone generated by the differential tone-relay 110 is heardby the calling subscriber who is informed thereby that he may now givethe desired number to the operator.

Relay 116 falls back shortly and opens the circuit of relay 115 inaddition to stopping the generating of tone current, whereupon relay 115falls back and connects conductors 118 and 119 to the operatorstelephone set. At the time this connection is made, the operatorstelephone set is shortcircuit-ed by contacts of relay 109, which relaywas cnergized through make contacts of relay 115, so that the charge onthe associated talking condenser is equalized with the potentialdifierence across conductors 118 and 119 in order to shield the operatorfrom disagreeable noises in her head set. Relay 109 falls back aninstant later and places the operators telephone set in communicativeconnection with the calling subscriber.

Registration of desired number Upon hearing the number desired by thecalling subscriber, which number, as hereinbetore assumed is 7945, theoperator depresses the digit keys of her key-set correspon ding to therespective digits of the number. It will be noted that the fourconductors associated with the digit keys are designated A, B, C and D.The operation of a given digit key results in the grounding of one ormore of these conductors. As can be seen in reading the drawings, theconductors grounded responsive to the operation of each key have beennoted in parentheses above each key.

WVhen the operator depresses the #7 key, the A conductor is grounded,operating relay A1 of the thousands register TH, Fig. 4, relay 127 beingoperated at this time from the grounded release trunk conductor 26through contact and armature of release relay 114 and the inner uppercontacts of the transfer relay 126. Upon operating, relay A1 locksitself to conductor 123 through transfer relay 126, but relay 126 doesnot opcrate until the initial circuit of relay A1 is opened, beingshort-circuited until this opening occurs when the digit key #7 isreleased.

hen the #7 key is released, relay 126 operates in series with relay A1(which latter relay remains operated) and at its inner upper armaturedisconnects the connecting relay 127, whereupon relays A1D1 aredisconnected from the conductors A to D. At its uppermost armature,relay 126 places ground upon conductor 122 through contacts of relay129, operating relay 113, Fig. 3, to open a point in the switch-throughcircuit to be hereinafter described and to place a multiple groundconnection on release trunk conductor 26 by way of conductor 26. At itsmiddle upper armature, relay 126 extends a ground potential to therelays of the hundreds register H, operating relay 131 to connect theconductors A, B, C and D to the relays A2, B2, C2 and D2, respectively.

Now, when the operator depresses the #9 key to register the hundredsdigit 9, conduc tor C is grounded, operating relay C2. This relay locksup in series with relay 130 which remains short-circurted as long as thekey is depressed and operates as soon as the key is released. Relay 130,in addition to extending a ground potential to the tens register T tocause relay 135 to operate, disconnects relay 131 and places a furthermultiple ground connection upon conductor 122.

When the tens digit 4 is registered by depression of the #4 key, relaysB3 and C3 are operated over conductors B and C, whereupon they look upin series with relay 134, which relay operates when the key is releasedand transfers the control to the units register U by releasing relay 135and operating relay 139. A further multiple ground connection is made toconductor 122 at the upper armature of relay 134-.

When the units digit 5 is registered by the depression of the #5 key,relays B4 and D4 operate over conductors B and D and lock up in serieswith relay 138, which operates when the key is released to open thecircuit of relay 139 and place a still further multiple groundconnection upon conductor 122.

Transmission of numbers Having finished setting up the number, theoperator depresses the St-art key, Fig. 3,

whereupon start relay 112 is operated through contacts of relay 108 andthrough the lower winding of relay 111. Relay 112 closes a lockingcircuit for itself to conductor 26 at its inner-upper armature, at thesame time disconnecting the upper winding of relay 111 from conductor26. However, relay 111 remains operated through its lower winding untilthe start key is released, whereupon it falls back and opens the circuitof relay 108, at the same time replacing ground on the associatedcontacts in the bank of wiper 125 of the distributor switch DS. Relay108 falls back and disconnects wiper 125 from the associated operatingmagnet, at the same time severing all connections between the operatorscommon equipment and the sender #1 and closing the associated point inthe chain circuit of startrelay 116, so as to enable the distributorswitch DS to operate again to connect the operators head set to anothersender which may have been taken for use in the meantime.

As a result of the operation of start relay 112, the switch-throughcircuit to be hereinafter described is prepared at the upper armaears ofrelay 112, and at the middle armature thereof ground is placed from theinner contacts of relay 113 upon the start conductor 121 in order tostart the stepping action of the counting switch CS, Fig. 5, under thecon trol of the marginal relay 142 associated with the interrupter I.

It may be pointed out at this time that the inte *rupter 1 is firststarted into operation upon the seizure of the sender when the groundpotential is placed upon release conductor 26 and consequently upon theconductor 26'. This results in a closure of a circuit through the magnetWinding of the in terrupter I and through the marginal stepping relay142 in series. Relay 142 does not operate in series with the magnetwinding of the interrupter I. But, upon the energization of this magnetwinding, the weighted pendulum is drawn over to the right, shortcircuiting the magnet winding of the interrupter, whereupon theinterrupter magnet deenergizes and the stepping relay 142 energizes.When the pendulum swings to the left, it again includes the magnetwinding of the interrupter in circuit, whereupon relay 142 falls back.As the interrupter I continues to operate, the marginal impulse relay142 is operated each time the pendulum swings to the right, and theinterrupter contacts of the interrupter I are opened each time thependulum swings to the left.

However, the operation of the interrupter I is ineffective and theoperation of the stepping relay 142 is ineffective likewise until startconductor 121 is grounded, as before described, upon the depression ofthe start key by the operator, from which time each deenergization ofthe stepping relay 142 results in an operation of the operating magnetof the counting switch OS from conductor 121 through contacts of stoprelay 144. The wipers 145 and 146 of the counting switch CS are advancedonly upon the back stroke of the operating magnet, and they consequentlyremain in the position shown upon the first energization of the magnet.When the pendulum of the interrupter I swings to the right and opens theoperating magnet circuit by energizing stepping relay 142, the operatingmagnet of the counting switch OS falls back and advances the wipers 145and 146 one step, whereupon pick-up wiper 145 encounters a groundedcontact, closing a circuit for pick-up relay 143. Pick-up relay 143 opcrates and prepares a locking circuit for stop relay 144 at its lowerarmature; places a further multiple ground connection upon conductor 122at its upper amature; and at its inner-upper armature it removes oneground connection from the outgoing impulse conductor 28, leaving theconductor grounded only through the contacts of the interrupter I. Now,with the circuit in this condition, each time the pendulum of theinterrupter I swings to the left, it sends an impulse by removing groundfrom conductor 28 to deenergize the line relay of the selector D,Fig. 1. The operating magnet of the counting switch CS is reoperated bythe deenergization of the stepping relay 142, so that each time thependulum swings to the right relay 142 reoperates and drops back theoperating magnet to advance wipers 145 and 146 another step.

hen the wipers of the counting switch are advanced again at the end ofthe transmission of the impulse, wiper 146 encounters the bank contactsin which the first stop conductor terminates, which stop conductor isgrounded only in case the digit being transmitted is the digit 1. Thedigit being transmitted in this case is the digit 7, stored on thethousands register TH, Fig. 4, from which it follows that the #7conductor is grounded instead of the :ttl conductor. The #7 conductor isgrounded at this time through the lower armature and resting contact oftransfer relay 129, Fig. 4, right-hand armature and make contact ofrelay A1, inner-righthand armature and resting contact of relay B2,inner armature and resting contact of relay C1, and inner armature andresting contact of relay D1. That being the case, the sending operationcontinues and the advance of the counting switch CS continues untilseven impulses have been sent by the interrupter I over the outgoingimpulse conductor 28. At the end of the seventh impulse,

' wipers 145 and 146 are advanced again and 7 the lower contacts ofrelay 143; closes a reground connection upon conduct-or 122 at stillanother armature; and at its uppermost armature it disconnects theoperating magnet of the counting switch CS from the impulse circuitcontrolled by the stepping relay 142.

Responsive to the closure of the restoring circuit of the countingswitch CS at the inner upper contacts of relay 144, theself-interrupting operating magnet of the counting switch operatesrapidly in a buzzer-iike manner and the wipers 145 and 146 are advanceduntil they stand in the position shown in the drawings, whereupon theaction ceases due to the fact that the normal contact in the bank ofwiper 145 is ungrounded. At this time, the circuit of the slow-actingpick-up relay 143 is opened, with the result that the relay falls backshortly and opens the locking circuit of relay 144, which relay shortlyfalls back to start the transmission of the hundreds digit 9.

Vhen the circuit of stop relay 144 is closed to end the transmission ofthe thousands digit, a parallel circuit is closed over conductor 120 andthrough contacts of relay 129 for relay 128, Fig. 4. Relay 128 operatesand locks itself to conductor 123 in series with relay 129, which latterrelay remains shortcircuited until the locking circuit of relay 144 isopened by relay 143, whereupon relay 129 energizes in series with relay128 and transfers the conductor 120 to relay 132 of the hundredsregister H.

The sendin operation proceeds for the second digit in the same manner asdescribed in connection with the first digit and is terminated at theend of the transmission of nine impulses upon the cnergization of stoprelay 144 when wiper 146 encounters the bank contact in which the stopconductor #9 terminates. The stop conductor #9 is grounded at this timethrough the lower armature and make contact of relay 129, through thelower armature and resting contact of relay 133, through the right-handarmature and resting contact of relay A2, through the outer-right-handarmature and resting contact of relay B2, through the outer-right-handarmature and make contact of relay C2, and then through the thirdrighthand armature and resting contact of relay D2.

Relay 132 is energized at this time in multiple with the stop relay 144and locks itself in series with relay 133, which latter relay operates,when the circuit of the stop relay 144 is opened, and transfersconductor 120 to relay 136 of the tens register T. The stopping grouudpotential is shifted at the lower ace terminates.

contacts of relay 133 to the register relay of he tens register.

lVhen the transmission of the tens digit takes place, the operation isthe same as described hereinbefore until stop relay 14% operates at theend of the fourth interruption in the outgoing control circuit whenwiper 1 16 of the counting switch CS encounters the bank contact inwhich stop conductor 1 Stop conductor is grounded, at this time, throughthe armature and resting contact oi relay A3 and the armatures and makecontacts of the operated relays B3 and C3 of the tens register. Relays136 and 13'! are operated in a manner similar to relays 132 and 133 totransfer the control to the units register U.

The transmission of the units digit next takes place and is terminatedupon the energization of stop relay 14 1 at the end of th fifthinterruption in the outgoing impulse conductor 28 when wiper 146 engagesthe bank contact in which stop conductor #5 terminates, stop conductor#5 being grounded at this time through contacts of the nonoperatedrelays A and C4 and the operated relay B 1 and De.

Freeing the sender It will be noted that each of the relays 129, 133,13'? and 1 11, upon operating, removes ground at one point from themultiplygrounded conductor 122. Now, when rela 1 1-1-1 operates upon theopening of the circuit of slow-acting stop relay 144, when pick-up byremoving ground from conductor 26 at one point, and closes theswitch-through circuit through contacts of the operated relay 112 andover conductor 27. This circuit includes the switch wiper of the senderselector SS, Fig. 1, armature 19 and make contact of relay 17, and thewinding of switch through relay 1. Relay 4 operates and locks itself torelease trunk conductor 3 at its armature 5 and make contact, and atarmatures 6 and 7, it disconnects the incom. g trunk conductors 1 and 2from the wind; ofthe battery feed elay 8 and extends th n to thecorresponding conductors of the connection established through theselector D. As a result of this, battery teed relay 8 falls ark and isfollowed by the falling back f relay '10 and consequently relay 1'? todisconnect the wipers of the sender selector SS to free the sender. Theestablished connection is now held up over the line of the substation11.

The falling back of relay 17 results in the removal of groundfrom therelease trunk conductor 26. This results inthe deenergization of relay112, Fig. 3, which is locked up to conductor 26 and the deenergizationof relays 126, 128 and 129, Fig. 4, which are locked up to conductor 26over conductor 123 ant through the armature and resting contact of relay11 1. As a result of the deenergization of relay 126, relays 130, 132and 133 of the hundreds register H dcenergize and in turn cause thedeenergization of the relays 132, 136 and 137 of the tens register T,which is followed by the deenergization of relays 138, 140 and 1 11 ofthe units register U. The operation of the interrupter I ceases as aresult of the removal of ground potential from conductor 26.

The sender is now at normal and may be seized again for use in anothercall.

Selector operafion The operation of the automatic switches employed inestablishing the connection in response to the trains of impulsestransmitted by the sender over conductor 28 will now be described byfirst detailing the operation of the selector D in response to the firstim pulse train. Returning now to the point in the description where therelay 17 first operated to connect up the wipers of the sender selectorSS, it will be noted that the connection of the impulsing wiper atarmature 2 tothe positive talking conductor connects ground theretosince conductor 28 is grounded through resting contact and armature ofrelay 143, Fig. 5. This ground is connected to the winding'of line relay30 of selector D, by way ofarmature and resting contact of switchingrelay 11 of the selector. This results in the operation of the linerelay and the completion of the circuit of release relay 31 from groundby way of armature 1 1 and resting contact of switching relay 41 througharmature and make contact of line relay 30. Release relay 31 operates,at its armature 32, connects ground to the release trunk conductor 3and, at its armature 33, opens the release magnet circuit and preparesthe impulsing circuit for the vertical magnet through the series relay34:.

Each subsequent removal of ground from conductor 28 by the interrupterI, Fig. 5, as has been explained, results in the deenergization of relay30 and since, in the assumed case, there are seven momentary removals ofground potential from the conductor'28, relay 3O deenergizes seventimes. In so doing, relay 3O completes the circuit for the verticalmagnet 36 seven times in series with the slowto-release series relay 34.Relay 34 operates in'series with the vertical magnet 36 upon the firstimpulse and remains operated through the entire series because of itsslowto-release characteristic. Vertical magnet 36, however, follows theimpulses and With each operation elevates the wipers 46, 47 and t8 ofthe selector D one step.

l i hen the switch shaft has been elevated one step, the verticaloff-normal springs 87 close and complete the circuit of the rotaryinterrupter relay 37 from grounded release trunk conductor 3, throughmake contact and armature 35 oi relay 34:, closed vertical ottnormalsprings 37, and thence through the winding of relay 37 to battery. Relay3? hereupon operates, at its armature 3S prepares the circuit for therotary magnet to and, at armature 39, locks itself through the selfinterrupting springs of rotary magnet lO to ground at armature 4% of theswitch switching relay l1.

After the seven removals of ground "from the conductor 28, there is aninterval when no interrupt-ions take place since ground is maintained onconductor 28 by step relay 144:, Fig. 5, during the time the countingswitch CS is being returned to its normal position. Relay 80 0t selectorD remains in its operated position during this interval and series relay34c releases a short time after the last deenergization oi relay 30, atits armature 35 opening the initial energizing circuit of the rotaryinterrupter relay 37 and connecting grounded release trunk conductor 3to the winning of the rotary magnet 40, whereupon rotary magnet l0operates and rotates the switch shaft and wipers one step. Thisoperation or the rotary magnet l0 opens the locking circuit of rotaryinterrupter relay 37, which relay tnence deenergizes and opens thecircuit of the magnet 10. Further stepping of the wipers -16 to as byrotation of the switch shaft is dependent upon the condition or thetrunk line with which the wipers are in engagcment as a result of thefirst rotary step. 7 I the tr .nk with whose contacts the wipers l6 toas are in engagement is busy, ground potential will be upon the testcontact there of and will be connected to the winding of the rotaryinterrupter relay 37 by way oi" test wiper 47, armature l3 and restingcontact t switching relay 1- self interrupting springs of rotary magnet40, vertical ofi-normal springs 37', and tience through the winding ofthe rotary interrupter relay 37. Thereupon rotary interrupter relay 37operates and at ar1nat-ure'38 again completes the circuit i'or rotarymagnet- 4:0, whereupon the shaft and wipers are rotated another step. Itwill be noted that, during this time, the circuit of switching relay 11is complete from grounded release trunk conductor, through the eleventhrotary position contacts 29, .ding of relay 41, through self interruptsprings of rotary magnet 40 and vertical ottnormal springs 37, windingof relay 37 to battery. However, when relay 37 is in its operatedposition, the winding of relay 4-1 is short-circuited from ground by wayof armature l4: and resting contact of relay 4:1, and armature 39 andmake contact of relay 37. Ground potential encountered upon busy testcontacts by the test wiper 4C7 also short-circuits the relay 41 toprevent its operation when relay 37 releases.

Each time the private wiper 47 engages a grounded test contact the relay37 and consequently the rotary magnet t0 are operated to rotate thewipers into engagement with the next set of bank contacts. This actionwill continue until wiper 47 engages an ungrounded test contactassociated with an idle trunk or until tl e eleventh rotary step hastaken place if all trunks are busy.

Should all of the trunks outgoing from the selector D be busy and theselector advances to eleventh rotary position, cam spring 29 is movedinto engagement with its make contact to complete the circuit of busyrelay 1a from grounded release trunk conductor 3, cam pring 29 and itsmake contact, armature 6 and resting contact of relay t, and winding ofrelay 14- to battery. Relay 14L thereupon operates and its armature 15looks itself to grounded release trunk conductor 3, at the same timeopenin the circuit of relay 17, which latter relay falls back anddisconnects the sender from selector D. Relay 14, at its armatur 16,connects tne secondary winding of the busy tone transformer T in thesubstation. battery teed circuit so that the calling subscriber isfurnished a busy tone to inform him that the desired connection cannotbe established at this time.

The disconnection of the sender from the select: D allows the sender torelease without having to transmit the remaining impulses. Thatdisconnection also results in the opening of the circuit of line relay30 of the selector D, which relay then falls back and opens bile circuitof release relay 31. Relay 31 falls back after an interval and in sodoing completes the c'- cuit of the selector release magnet. lhe r leasemagnet thereupon operates to restore the selector D in the well-knownmanner.

For the purpose of this description, it will be assumed that the trunkcomprising conductors :32, 53 and 54:, which are connected to contacts49, 50 and 51, respectively, is the first idle trunk to be eircountercd.l t hen this occurs, relay ll will no longer be shortcircuited and itwill operate in series with the rotary interrupter relay 37 over thepreviously traced circuit. Rel 1y 37, however, because of the relativelyh .1 resistance of re ay 41 does not operatively energize in seriestherewith.

Upon the operation of elay t1, the talking conductors of the selector Dare connected through to the trunir conductors 52 and t at armatures 42and as of relay 41, line relay 30 and release a leS and the circuit orrelay 81 are opened at armatures l5 and 44:,

relay-185; Thisrconnection ofrgroundvto conductor. 52".completeszthecircuit for; relay. 14: inithetrnnkarelay groupsRG, Ei'grl', byrway' ofbank. contact 49; Wiperi 16, make: contact and armature 42:. of; relay11 armature 6 and: resting.- contaet of relay 1; of? the? trunk relay:-group .RG; and. thence: through the winding; of; re1aya14; tobatteryRelay 1% thereupon :operates,and;at2armature:15, locksitself: togrounded arelease 1 trunk conductor 3 1 and; at armature 16,oonneotsthesecondary windingrof the busy: tone: transformer T in 1serieswith: the battery feed relay 8, so as to superiinpose busy tone.upon-:the-trunk conductors 11 and Qrthrough thewinding: of the: battery.feedi relay; 8? to lIOlllfYz the calling.

subscriber at substation A that the desired liner is. busy; I

In completing; its locking: circuit atarin'a-- ture 15;relay 1&1opens'the'circuit of relay 1-7 which relay then deenergizesand"d1sconnects--the Wipersof the senderselector SS from the connector:Ezto free-the sendenwithout its having tozsend the last: series Of'ln'kpulses. The disconnection of the impulse wiper from tliepositive'talking conductor through 1 the selector,- results in the"disconnectioirof' ground fronrther lower Winding. ottheline relayofwtheconnector-E,wh1cha relay thereupondee-nergizes and opens thecircuit of: the release relay: 61, whiclnafter an interval; releases andat its armature 64. and resting conta ct completes the circuit of: thereleaser-mag11et=7l= by- Way" of: armature- (39 a-ndresting; eontactotrelay 67 and'ver ticaloff-normal springs-70. The releasemag'f netthereupon operateswandrestores tl1e-connector switch I E toitsnormalposition; in the usualimannen The removal. of groundvfrom; the.release-trunk conductor-F53by the deen-- ergizationof the release relay;61- of the con-v nector opens the circuit of. the switching: relay 41 0ftheselector Dgwhich relay there-- upon releases and; at armature l landrresting contact completes the circuit for the selector releasemagnet. by Way of? armature and resting; contact ofhne relay 30,armature and resting; contactoflrelay 31, and vertical olfnormal springs33'. The selector. release magnet thereupon operates and 2 restores theselector D to its normal'position-in :the Well known manner.

RelaysS, 10 and: 14 of the trunk relay group are now theonly relays intheir operated positions-and-they remainso as-long as the subscriberatthe substation Annaint-ains his receiver oif the receiver hook;

- Assuming, however, that the desired l1ne is idle at: thetimetheconnector Wipers- 102' to 104 are placed in engagement with the co1'1tacts'102 to 104; of the desired line, Wiper 103-does not encounter groundand no circuit iscompleted, therefore; for the relay 72. When relay 85deenergiz-esafter thetransmission of the four impulses, at: restingcontact and armature 87 thereof; the circuit: for the upper Windingofthe switch througli ree lay 95' is completed from grounded releasetrunk-conductor 53 by Way of armatureand resting contact: of relay 72;thence through. theupper Wihding of? the relay 95,

to the: Winding of the cut-off? relay of the lineswitch ofthedesirediline'by way-of armaiture 87 and resting contact ofrelay wiper103, and test c0ntactil03. Thecut-offirelay of the called subscriberslincswitch operates" inlth'e well known manner to disconnect the linerelay thereof from the line to prevent the operation of that relayshould the called subscriber: desire toinitiate acall before his callingbells have been operated; Thatout of relay also connects ground-to thetestieon tact 103' to inarkthe-called line busy to'all other connectors,by placing ground on-theinultipled test contacts-- in all] the banksthereof;

Relay operates when its circuit is so completed and mo ves itsarmatures- -96'1to 1101*, r IHClHS' VQ,' lnto their operated positions;

thereby; at its armature- 98, locking itself? through: itslower Windingto the comniom lockingconductor 63 r 'Dhennpul'sing circuit in theconnector: is now connected byway ofvarmaturei99 and its make contactitothe rotary magnetz79 of the ringin frequency selector RF S1 Vhen theicxt' and ilast series of interruptionsoccnr in the circuit: of theline. relay: 55; live: ground: impulsesaretransmitted to the rotarymag;- net 79 of the'ringing: frequency selector,. and, as i a: result-3.the wipers; 79 and' SO" are stepped into engagement; with the. fiftliisett ofzcontacts: of their banks Relay 8-5 oper-- ates in multiple';Witlrt'he rotary 111agnet's79.

to. remove ground: from conductor 86 so: thatrelay: 57, Whosecirciut 1spreparede'byr the off-nonnalT'spi-ings 66 ot-the. ringing ire-.-

quencysele'ctor: RF'S- \vhen th at s-witeh makes its first: step; cannotoperate until :7 the. in

pulse transmission" has' been completeda. Now, when relay 85 releases atthe end of the the two"Win-dingsof: the relay 55" over the:

talking; conductors 52 and 54." At the same time this-takes placeythesender connects grounditothe switch Wiper of tlie sender selector: SSconsequentlycompleting thecircuit of the relay 1 which operates;as-preii ously explained,- to connectthe trunloconductors 1 and 2 overthe talking: conductors relay 89 operates. I

of thesele ctor D to the talking conductors 52 and 54 of the connectortru'nln This connection of the talking conductors extends the circuit ofthe .battery-feed-line relay oi. the connector E .over the-callingsubscribefls loo) therelr maintainin the rela 55 0 er-,

-- and make contact of switching relay and normally engaged contactscontrolled by ar mature 93 of relay 89, to inform the calling subscriberthat the bells at the called station are now being rung. 7

Since it has been assumed that switch RFS received five impulses and thewipers 79 and are in. engagement with their fifth bank contacts, 66cycle ringing current will be applied tothe called subscribers bellsover the negative talkingconductor by way of wiper 79 of switch RFS,armature 7 3 and make contact of relay 72, resting contact andarmatureof ring cut-oil relay 89, armature 96 and make contact of relay 95, linewiper 102, bank contact 102", over the called subscribers negative lineconductor and through the subscribers calling bells to ground. The 66cycle ringing current is projectedover the just described circuit fromsuperimposed battery of a 66 cycle ringing current generator.

The called subscriber hearing the ringing of his bell, removes thereceiver from the switch hook and thereby completes the loop circuitover the line terminating in the contacts 102 and 104, therebycompleting the circuit for the upper winding of the ring cutofl relayfrom the superimposed battery, over the ringing circuit just describedwith the exception of the bells, through contacts controlled by thecalled subscribers switch hook,

over the positive line conductor, bank contact 104, positive line wiper104, make contact and armature of relay 95, armature 93 and restingcontact of relay 89, make contact and armature 78 of relay 72, wiper 80of switch RFS,fifth bank contact and jumper to first bank contact, andupper winding of relay 89 to grounded common locking conductor 63'.Relay 89 operates in this circuit, at its armature 91 looks itself up tocommon locking conductor 63 through its lower winding, and at armatures90 and 90 opens the ringing circuit and extends the called subscribersloop to the windings of the back bridge relay 67. At armature 92, relay89 prepares a substitute locking circuit for itself which will beindependent of the armature 63 of release relay 61 when the back bridgerelay 67 operates, which it does shortly after the ring cut-off to theconnector IE, it willbe noted that as before explained, the battery feedsource-P through the windings of relay 8 is disconnected from the trunkconductors 1 and 2 to thereby substitute the battery feed source P1 forthe source P. As before explained this disconnection of relay 8 resultsin the freeing of the sender for use in the extension of other 1 calls.v

The connection as now describedin the trunk relay group, in theselector'D, and in the connector E, is maintained as long as the twostations remain in talking connection with each other, and no changetakes place until one or both of the subscribers replace their recciverson the receiver hooks.

Release "of connection Should'the calling subscriber at substation A'bethe first to replace his receiver upon the receiverhook, the-loopcircuit over conductors 1 and 2 is opened and consequently results inthe release of line relay 55 of the connector E. Relay 55,-in releasing,at its armature 56 opens the circuit of release relay 61, which relayafter an interval deenergizes and at its armature 62 removes ground fromthe release trunk conductor 53, thereby opening the holding circuit forswitching relay 11 of the selector D. At its armature 63, relay 61removes one ground connection from holding conductor 63 ground beingmaintained thereonthrough armature 68 and make contact of relay 67 andgrounded armature 92 and make contact of the ring cut-off relay 89. Atits armature 64, relay 61 prepares the circuit for the release magnet 71of the connector E, the circuit for release of the magnet beingmaintained open at armature 69 of back bridge relay 67. At armature 65,relay 61 completes the circuit for release magnet 80 of the ringingfrequency selecting switch RFS from grounded armature 60 and makecontact of relay 57. V

The completion of the circuit for the release magnet 80 of the switchRFS results in the return of wipers 79 and 80 thereof to their normalposition, in which position the switch opens its off-normal contacts 66,thereby opening the series circuit of relays 57 and'72. Relays 57 and "2thereupon deenergize, and relay 57 at armature 60 opens the circuit ofthe release magnet 80 of the switch RFS. Further release of theconnector E is dependent upon the replacement of the receiver upon thereceiver hook at the called station. r

In the selector D, relay 41 falls back when ground is removed from therelease trunk conductor 53, and, in so doing, at its armature ll andresting contact completes the circuit or the selector release magnet byway of arni-ature' and resting contact of relay 30, armature and restingcontact of relay 31, and through vertical off-normal springs The releasemagnet of the selector 1) operates, and, in the well. known manner,restores the switch-shaft and wipers to their normal position, therebyeopeningt-he oil-normal springs 33 to, open the release magnet circuit.

The removalsot ground from the release trunk conductor 53 of theconnector E results in the removal oi": ground from the release trunkconductor 3 and release trunk conductor 3. The locking circuit of relays4 and 14 are thereby opened and these relays release, restoring thetrunk relay group RG to its normal position, or that in which the relaysthereof are shown in Fig. 1.

The replacement of the called subscribers receiver upon the receiverhook results in the openingwof the circuit of the back bridge relay 67,which relay thereupon deenergizcs and, in so doing, atarmature 6S,removes ground from; the common locking conductor (53!, and at itsarmature 59 and resting contact,- completes the circuit of the connectorrelease magnet 71. Relays S9 and 95, which are locked up through theirlower windings to the common conductor 63, deenergize as a result oftheremoval of ground from that conductor.

Release magnet 71 operates, when its circuit is completed at armature 69and resting contact of relay 6, and in the well known manner restoresthe connector to its normal position. Theequipment is now in readinessto be taken into use for-the establishment of another connection.

Ringing source and application sender,- comprises five or less impulses,one

ofthe five sources of ringing current will be applied to the calledsubsoribers bells by way of wiper 79 and then over the negative talkinconductor. If the" rin ing frequency digit comprises more than fiveimpulses, the rimging current will be applied over the positive talkingconductor to'the called subscribers' station by way of wiper 80. This isthe well kn-own manner of code ringing in the case of a ten-partylinetelephone system.

Metering When the calling subscribers lineswitch C finds an idle trunkupon the subscriber at substation A initiating a call, as has beenexplained, the current for the calling subscribers circuit is suppliedfrom the battery feed source P. Since, as explained, this source is onewhich at predetermined intervals reverses the polarity of this currentin the calling subscribers circuit, the operation of the elapsed timemeter M is commenced substantially at the time when the callingsubscriber removes his receiver from the receiver hook since the huntingtime of the lineswitch C is practically negligible. When the desiredline is found to be idle by the connector E, the battery teed source P1is substituted for the source P, and the operation of the elapsed timemeter M continues until the calling subscriber replaces his receiverupon the receiver hook.

It will be remembered, that, in the case where the selector D could findno idle trunk leading to a succeeding switch and in the case where theconnector E found the desired line to be busy, the relays 8, and 1% ofthe relay group HG were held operated while the selector D and theconnector E were released. That condition resulted in the application ofbusy tone to the calling subscribers line by the superimposing of busytone current upon the current from the source P. Inasmuch as the currentfrom the source P is applied to the subscribers circuit as long as thesubscribers receiver remains oii the hook, the. operation of the elapsedtime meter M takes place until the subscribers circuit is opened by thereplacement of the receiver on the receiver hook. In this manner thecalling subscriber is charged for substantially all of the time histelephone is in use in the establishment of a connection.

lVhen the subscriber at substation A is the recipient of a call, thesubscribers meter is not operated since no current reversals take placeover the conductors 1 and 2 inasmuch as the talking current is suppliedthrough the back brid e relay of the connector in use, which relay hasits windings connected direct to'a constant polarity source as may beseen in the case of the back bridge relay 67 of the connector E.

The invention having been thus described,

- what is considered new and what is desired to have protected byLetters Patent will be pointed out more specifically in the claims whichfollow.

WVhat is claimed is:

1. In a telephone system, a calling line terminating in an exchange, ameter for said line, a trunk, means responsive to the initiation of acall over said calling line for connecting said line and trunk together,and

means responsive to said connection for periodically operating saidmeter as long as said connection is maintained.

2. In a telephone system, a calling line, a meter therefor, a trunk, asource of periodically pole-changing current, and means responsive tothe initiation of a call over said line for connecting said line to saidtrunk and connecting said current source to said line, said sourceconnected to said line to sup ply talking current to said line andperiodically operate said meter.

3. In a telephone system, a calling line, a meter therefor, a trunkterminating in a se lector, a source of periodically pole-changingcurrent associated with said trunk, a plurality of connectors, meansresponsive to the ini tiation of a call over said line for connectingsaid line to said trunk and connecting said current surce to said linefor periodically operating said meter, means for operating said selectorto cause it to automatically hunt for an idle one of said connectors,and means operated by said selector when it finds all of said connectorsbusy for supplying a busy tone to said line While maintaining theperiodic operation of said meter.

4. In a semi-automatic telephone system, a calling line, a metertherefor, a called line, a trunk terminating in a selector, a source ofperiodically pole-changing current associ ated with said trunk, meansresponsive to the initiation of a call over said calling line forconnecting said line to said trunk and connecting said current source tosaid calling line for periodically operating said meter, a connector, anoperators position, means associated with said trunk and responsive tothe connection of said calling line with said trunk for connecting saidtrunk to said operators position, said current source supplying talkingcurrent to said calling line, means associated with said position foroperating said selector to extend said calling line to said connectorand for thereafter operating said connector to extend said calling lineto said called line, a second source of periodically polechangingcurrent associated with said connector, and means responsive to theextension of said calling line to said called line.

for transferring the periodic operation of said meter from the firstmentioned source of pole-changing current to said second 5. In a tele)hone s 'stem a callins line a meter therefor, a called line, a trunkterto said trunk for periodically operating said meter until saidcalling line is connected with said called line, means responsive to theconnection of said calling line with said called line for transferringthe operation of said meter to said connector, and means in saidconnector for thereafter periodically operating said meter.

6. In a telephone system, a calling line, a

meter therefor, a trunk, non-numerical means for connecting said linewith said trunk, a train of switches accessible over said trunk, meansfor operating said switches for extending a call from said line, andmeans responsive to the connection of said line with said trunk forperiodically operating said meter as long as said connection ismaintained regardless of the success of said train of switches inextending the call.

7. In a telephone system, a calling line, a meter therefor, a calledline, a trunk, means responsive to the intiation of a call over saidcalling line for connecting said calling line with said trunk, means forconnecting said trunk with said called line provided said called line isidle, and means for periodically operating said meter responsive to theconnection of said calling line with said trunk and for continuing thatperiodic operation as long as said calling line is connected with saidtrunk regardless of whether or not said trunk is connected with saidcalled line.

8. In a telephone system, a calling line, a

meter therefor, a two section trunk, a first source of periodicallypole-changing current normally connected to the first section, a secondsource of periodically pole-changing current, means for connecting saidline with said first section to commence the periodic operation of saidmeter by said first current source, means for connecting said secondcurrent source to the second section of said trunk, and means fordisconnecting said first section from said first source and connectingsaid first section to said second section to transfer the periodicoperation of said meter to said second source.

9. In a telephone system, a calling line, a meter therefor, a calledline, a two portion trunk terminating in a selector, a first source ofperiodically pole-changing current normally connected with one portionof said trunk, means responsive to the initiation of a call over saidcalling line for connecting said calling line with said one trunkportion to thereby connect said first currentsource to said line forperiodically operating said meter, a connector, a second source ofpole-changing current associated with said connector, means foroperating said selector to extend the other portion of said trunk tosaid connector and for thereafter operating said connector to extendsaid other trunk portion to said called line, means in said connectoroperating automatically if said called line is idle when said othertrunk portion is extended thereto to connect said other trunk portion tosaid called line and to connect said second current source to said othertrunk portion, and means for thereafter disconnecting said one trunkport-ion from said first source and connecting said one portion to saidother portion to transfer the periodic operation of said meter to saidsecond source.

10. In a telephone system, a callin line, a meter therefor, a calledline, a two portion trunk terminating in a selector, a first source ofperiodically pole-changing current normally connected with one portionof said trunk, means responsive to the intiation of a call over saidcalling line for connecting said calling line with said one trunkportion to thereby connect said first current source to said line forperiodically operating said meter, a connector, a second source ofpolechanging current associated with said connect-or, means foroperating said selector to extend the other portion of said trunk tosaid connector and for thereafter operating said connector to extendsaid other trunk porti on to said called line, means in said connectoroperating automatically if said called line is idle when said othertrunk portion is ertended thereto to connect said other trunk portion tosaid called line and to connect said second current source to said othertrunk por tion, means for thereafter disconnecting said one trunkportion from said first source and connecting said one portion to saidother portion to transfer the periodic operation of said meter to saidsecond source, means in said connector for preventing the connection ofsaid other line and the connection of said second source to said otherportion if said called line is busy, and means responsive to theoperation of said preventing means for supplying said calling line witha busy tone while maintaining the periodic operation of said meter bysaid first source and for causing the release of said selector andconnector.

11. In a telephone system, a calling line, a meter therefor, a calledline, a trunk having a first section and a second section, a firstsource of pole-changing current normally connected to said firstsection, a second source of pole-changing current associated with saidsecond section, means for connecting said first trunk section with saidcalling line to connect said first current source to said calling lineto periodically operate said meter, means for connecting said secondsection to said called line and for connecting said second currentsource to said second section, and means for disconnecting said firstsection from said first source and for con trunk portion to said called'necting the two sections together to transfer the periodicoperationofssaid meter to said second source.

12. In a telephonesystem, acalling line,

a meteritherefor, a first'source ofperiodically pole-changing current,.a second source of periodically pole-changing current, means responsivetothe initiation ofacall over said line for connecting said first sourceto said line to periodically operate said meter, means for extending theinitiated call, and means for thereafter disconnecting said line fromsaid first source and connecting it to said second source to transferthe periodic operation of said meter to said second source.

13. In atelephone system, a calling line, a meter therefor, a firstsource of periodically pole changing current, a second source ofperiodically pole changing current, means responsive to the initiationof a call over said line for connecting said first source to said lineto periodically operate said meter, means for extending the initiatedcall provided no busy condition is encountered, means operable where theinitiated call is extended for' disconnecting said line from said firstsource and connecting said line to said second source to transfer theperiodic operation of said meter to said second source, and means forpreventing the operation of said last means if a busy condition isencountered, thereby maintaining the periodic operation of said meter bysaid first source.

14. In a telephone system, a calling subscribers station, a linetherefor, a meter associated with said line, a trunk having means forperiodically operating a meter, means responsive to the removal of thereceiver from the receiver hook at said station for connecting said lineto said trunk, said means thereupon periodically operating said meter.

15. In a telephone system, a calling line, a meter therefor, a trunkhaving a source of periodically pole-changing current associatedtherewith, and an automatic switch responsive to the removal of thereceiver from the receiver'hook at the substation of said line forconnecting said line to said trunk and said source of current, saidpole-changing current thereupon periodically operating said meter.

16. In a telephone system, a calling line provided with a meter, acalled line, a train of switches, a trunk incoming to the first switchof said train, means responsive to the initiation of a call over saidcalling line for connecting said calling line to said trunk, meansassociated with said trunk and rendered eifective by the connection ofthe calling line thereto for periodically operating said meter, meansfor operating the switches of said train successively to extend the callto said called line, and means responsive to the encountering of a busycondition by anyone CAI of said switches While attempting to extend thecall for supplying abusy tone to said calling line Without affecting theperiodic operation of said meter.

In Witness whereof, I hereunto subscribe my name this 5th day of April,A. D. 1930.

NORMAN H. SAUNDERS.

